After destroying the bioweapon known as Antares near the end of the first tournament, Shin Ikushima infiltrated the main building of Orion Corporation in an attempt to hunt down the company's CEO, Ranzou Kihara, in order to finish him off right then.
However, when he went to the chairman's office, there was no Ranzou, rather, there was only a young girl inside a cryogenic sleep chamber. Shin releases the girl from the chamber and runs off. Realizing that she lacks any memory of her past, Shin decided to adopt the girl, naming her Kei.
Ten years later, Kei, under guidance from Shin, grows up to become a beautiful young lady, and an accomplished black belt in Kyokushin karate. Kei still had no memory of her past prior to Shin saving her, but this did not bother her in the slightest.
Until one day, Kei encounters a mysterious woman named Eileen A., who claims to be a former employee of Orion. Eileen told Kei about the Orion Corporation and how Ranzou Kihara is the one holding the answers to her past, before eventually departing, leaving Kei with nothing but questions.
Several months after that fateful meeting, Orion announces the second Sentoki: Global Martial Arts tournament. Kei, along with her guardian and master Shin, decides to join the tournament to meet Ranzou Kihara and find more about her past.
